This proposal aims at elucidating the mechansims of hemoproteins and enzyme action using magnetic resonance spectral techniques. With human hemoglobins, the mode of oxygen binding, the interaction with organic phosphates, the relationship between the protein conformation and the heme spin-state, the mechanism of cooperative oxygenation, and the mechanism of aggregation of intracellular hemoglobin in sickle red blood cells will be studied. The arrangement and conformation of substrates at the catalytic sites of several phosphoryl transfer enzymes will be determined by paramagnetic probes using Cr 3 ion nucleotide complexes as substitution-inert, paramagnetic analogs of Mg 2 ion nucleotides. The role of metal ions in the catalytic mechanism of phosphoryl-transfer enzymes will thereby be clarified. Comparative nuclear relaxation studies of the conformation of enzyme-bound organic substrates to Mn 2 ion and Co 2 ion - carbonic anhydrases will be carried out to determine why the Mn 2 ion enzyme is less active. 31P-NMR studies of the intact human red blood cell and frog muscle are being pursued with a view to understand the role of free Mg 2 ion in providing the control signal for the regulation of metabolism in these cellular systems. A detailed understanding of the mechanism of purified proteins and intact cellular systems at the molecular level which is the ultimate aim of the proposed research is fundamental to a knowledge of the biochemical pathways of life and may provide new insights for the treatment of diseases arising from molecular abnormalities.